500 is fine for me, usually I do exceed the limit but I just sell epics commons and rares. I put stuff I don't use other than to sell for a higher price in the future in stash or on other chars. I gift the chests eggs or other items I don't want to beggars.
The stack to 999x ehh would like to hold 9999x but its fine, atleast its not 1x and fills your inv anymore.
Instead a search option; maybe change the favorite opt to not only disable trade and gift on it, but put it at the top of your inventory category. Heart 1 heart 2 so on, slot 1 slot 2. Each category starts from 1 which is first in your list. This would be faster than searching I think.